全文获取类型
收费全文 | 2676篇 |
免费 | 149篇 |
国内免费 | 1235篇 |
专业分类
安全科学 | 209篇 |
废物处理 | 150篇 |
环保管理 | 178篇 |
综合类 | 1668篇 |
基础理论 | 469篇 |
污染及防治 | 1056篇 |
评价与监测 | 137篇 |
社会与环境 | 92篇 |
灾害及防治 | 101篇 |
出版年
2024年 | 5篇 |
2023年 | 59篇 |
2022年 | 152篇 |
2021年 | 120篇 |
2020年 | 108篇 |
2019年 | 92篇 |
2018年 | 119篇 |
2017年 | 134篇 |
2016年 | 168篇 |
2015年 | 196篇 |
2014年 | 233篇 |
2013年 | 294篇 |
2012年 | 245篇 |
2011年 | 227篇 |
2010年 | 172篇 |
2009年 | 184篇 |
2008年 | 199篇 |
2007年 | 177篇 |
2006年 | 156篇 |
2005年 | 122篇 |
2004年 | 86篇 |
2003年 | 99篇 |
2002年 | 78篇 |
2001年 | 90篇 |
2000年 | 74篇 |
1999年 | 87篇 |
1998年 | 68篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 64篇 |
1994年 | 41篇 |
1993年 | 35篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1976年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有4060条查询结果,搜索用时 15 毫秒
841.
842.
Preliminary 3-D site-scale studies of radioactive colloid transport in the unsaturated zone at Yucca Mountain,Nevada 总被引:1,自引:0,他引:1
The U.S. Department of Energy (DOE) is actively investigating the technical feasibility of permanent disposal of high-level nuclear waste in a repository to be situated in the unsaturated zone (UZ) at Yucca Mountain (YM), Nevada. In this study we investigate, by means of numerical simulation, the transport of radioactive colloids under ambient conditions from the potential repository horizon to the water table. The site hydrology and the effects of the spatial distribution of hydraulic and transport properties in the Yucca Mountain subsurface are considered. The study of migration and retardation of colloids accounts for the complex processes in the unsaturated zone of Yucca Mountain, and includes advection, diffusion, hydrodynamic dispersion, kinetic colloid filtration, colloid straining, and radioactive decay. The results of the study indicate that the most important factors affecting colloid transport are the subsurface geology and site hydrology, i.e., the presence of faults (they dominate and control transport), fractures (the main migration pathways), and the relative distribution of zeolitic and vitric tuffs. The transport of colloids is strongly influenced by their size (as it affects diffusion into the matrix, straining at hydrogeologic unit interfaces, and transport velocity) and by the parameters of the kinetic-filtration model used for the simulations. Arrival times at the water table decrease with an increasing colloid size because of smaller diffusion, increased straining, and higher transport velocities. The importance of diffusion as a retardation mechanism increases with a decreasing colloid size, but appears to be minimal in large colloids. 相似文献
843.
Qianfeng Li Di Hu Sirakarn Leungsakul Richard M. Kamens 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9341-9352
This work merges kinetic models for α-pinene and d-limonene which were individually developed to predict secondary organic aerosol (SOA) formation from these compounds. Three major changes in the d-limonene and α-pinene combined mechanism were made. First, radical–radical reactions were integrated so that radicals formed from both individual mechanisms all reacted with each other. Second, all SOA model species from both compounds were used to calculate semi-volatile partitioning for new semi-volatiles formed in the gas phase. Third particle phase reactions for particle phase α-pinene and d-limonene aldehydes, carboxylic acids, etc. were integrated. Experiments with mixtures of α-pinene and d-limonene, nitric oxide (NO), nitrogen dioxide (NO2), and diurnal natural sunlight were carried out in a dual 270 m3 outdoor Teflon film chamber located in Pittsboro, NC. The model closely simulated the behavior and timing for α-pinene, d-limonene, NO, NO2, O3 and SOA. Model sensitivities were tested with respect to effects of d-limonene/α-pinene ratios, initial hydrocarbon to NOx (HC0/NOx) ratios, temperature, and light intensity. The results showed that SOA yield (YSOA) was very sensitive to initial d-limonene/α-pinene ratio and temperature. The model was also used to simulate remote atmospheric SOA conditions that hypothetically could result from diurnal emissions of α-pinene, d-limonene and NOx. We observed that the volatility of the simulated SOA material on the aging aerosol decreased with time, and this was consistent with chamber observations. Of additional importance was that our simulation did not show a loss of SOA during the daytime and this was consistent with observed measurements. 相似文献
844.
宁波市危险废物管理、处置现状和对策 总被引:1,自引:0,他引:1
对宁波市危险废物现状进行了调查,分析了危险废物的来源、产量、特征及存在的主要问题.在此基础上,提出了宁波市危险废物管理处置对策,具体包括:加强危险废物申报登记工作;健全宁波市危险废物管理法律体系和监督管理机构;建立合理的危险废物收费制度;源头控制危险废物污染和建设危险废物集中处置场等. 相似文献
845.
根据高浓度油脂废水生物降解处理采用酵母一级处理-SBR法二级处理的连续净化工艺的要求,使用规模为20 L的SBR反应器对城市生活污水处理用的活性污泥进行强制性驯化,并以驯化的活性污泥菌直接应用于SBR法处理含油废水.实验发现该小型SBR法的工艺技术方案可行,系统抗冲击负荷能力强,整个系统运行比较稳定,对于含高浓度油脂的油脂精练加工厂实际排放污水处理效果良好,油脂和COD的去除率分别连续稳定在95%和90%以上,出水水质指标达到国家一级排放标准的要求. 相似文献
846.
Twenty-eight PM2.5 samples collected in Summer (July 2002) and Winter (November 2002) at two sites in Beijing, China were analyzed using GC/MS to investigate the impact of meteorology and coal burning on the solvent extractable organic compounds (SEOC). The characteristics and abundance of the n-alkanes, polycyclic aromatic hydrocarbons (PAHs), n-fatty acids and n-alkanols were determined. Source identification was made using organic species as molecular markers. Semi-volatile compounds of alkanes and PAHs had much higher concentrations in winter than summer because of the large difference in the temperature between the seasons. Plant wax emission was a major contributor to n-alkanes in summer, but fossil fuel residue was a major source (>80%) in winter. The seasonal differences in the distribution of pentacyclic triterpanes clearly shows the impact of coal burning for space heating in winter. The yield of PAHs in winter (148 ng m(-3) at the urban site and 277 ng m(-3) at the suburban site) was six to eight times higher than that in summer and was found to be mainly from coal burning. Higher pollutant concentrations were measured at the suburban site than the urban site in winter due to the rapid expansion of the city limit and the relocation of factories from urban to suburban areas over the last two decades. 相似文献
847.
应用11种限制性内酶BamHⅠ、BstEⅡ、EcoRⅠ、EcoRⅤ、HindⅢ、KpnⅠ、PstⅠ、SalⅠ、SstⅠ、XbaⅠaⅠ和XⅠⅠ和XhoⅠ分别将中国棉铃虫核多角体病毒(单粒包埋HaSNPV)湖北株基因组D组DNA酶切为10、12、22、21、13、6、6、40、6、21、6个片段,并求得基因组大小平均为1什什Mr≈79.1×106.以家委核多角体病毒BmNPV多角体基因为探针,利用Southern杂交技术将病毒多角体基因定位在SalⅠ4.2×103b左右的片段上.与棉铃虫核多角体病毒其它株系酶切图谱比较结果表明,本株病毒与上海等株系及美洲棉铃虫核多角体病毒HaSNPVElkar株系酶切图谱相似,它们之间的条带数和大小差异较小,而与已发现的所有多粒包埋型病毒HaSNPV酶切图主谱差异较大.据此认为HaSNPV和HaMNPV属于基因型不同的两类病毒,而HaSNPV不同分离株的同源性很高 相似文献
848.
Peng Zhao Tong Zhu Baosheng Liang Min Hu Ling Kang Jicheng Gong 《Frontiers of Environmental Science & Engineering》2007,1(2):159-165
Agricultural activity is one of the most important sources of aerosol particles. To understand the mass distribution and sources of aerosol particles and their inorganic water-soluble ions in a suburb farmland of Beijing, particle samples were collected using a microorifice uniform deposit impactor (MOUDI) in the summer of 2004 in a suburb vegetable field. The distribution of the particles and their inorganic water-soluble ions in the diameter range of 0.18–18 μm were measured. The dominant fine particle ions were SO4 2?, NO3 ?, and NH4 +. The association of day-to-day variation of the concentration of these ions with temperature, humidity, and solar radiation suggested that they are formed by the reaction of NH3 released from the vegetable field with the acid species produced from photochemical reactions. Fine particle K+ is likely from vegetation emission and biomass burning. Coarse particles like Ca2+, Mg2+, NO3 ?, and SO4 2? are suggested to come from the mechanical process by which the soil particle entered the atmosphere, and from the reaction of the acid species at the surface of the soil particle. The results show that fertilizer and soil are important factors determining the aerosol particle over agricultural fields, and vegetable fields in suburban Beijing contribute significantly to the aerosol particle. 相似文献
849.
本文对1974年4月22日和1979年7月9日在江南水乡溧阳先后发生的两次中强地震的灾情进行回顾以及地方地震部门在抗震救灾中应发挥的作用进行总结,同时,对这两次中强震前的相关异常进行分析,这样可为我们今后的地震预报提供参考,也可为我们以后的抗震设防和抗震救灾提供借鉴。 相似文献
850.
胡庚松 《安全.健康和环境》2020,(1):58-60
以化工园区安全生产、事故防范、救援救灾为大背景,通过智慧监管、大数据分析、一体化指挥体系、救援圈建立、跨区域资源配置等方法理念,提出了推行化工园区防范救援救灾一体化建设思路。 相似文献